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iPTF Discovery of iPTF13efs, a Type II (possibly IIb) Supernova

ATel #5672; I. Arcavi, A. Gal-Yam, D. Tal, O. Yaron (WIS), Y. Cao (Caltech), D. Stern (JPL/Caltech), J. Sollerman, F. Taddia (OKC) and O. Smirnova (NOT) on behalf of the intermediate Palomar Transient Factory collaboration
on 17 Dec 2013; 20:40 UT
Credential Certification: Iair Arcavi (iarcavi@lcogt.net)

Subjects: Optical, Supernovae

The iPTF (ATel #4807) reports the discovery and classification of a Type II supernova (SN), iPTF13efs. The SN is located at RA = 07:55:26.19 and Dec = +52:48:17.9 (J2000), approximately 7 arcsec from the center of a redshift 0.04062 galaxy (SDSS, DR10). iPTF13efs was discovered on 2013 December 11 (UT dates used throughout) at m_R = 19.44+/-0.12 mag (corresponding to M_R = -16.74 at the galaxy redshift). The SN was not visible on images taken during December 2012. A spectrum was obtained on 2013 December 11 with the DEep Imaging Multi-Object Spectrograph (DEIMOS) mounted on the 10m Keck-II telescope, showing a broad H-alpha feature. The superfit program (Howell et al. 2005, ApJ 634, 1190) finds a good match to the Type II SN 1987K at 7 days after peak, with a redshift consistent with the likely host galaxy (z~0.04). An additional spectrum taken with the Andalucia Faint Object Spectrograph and Camera (ALFOSC) on the 2.5m Nordic Optical Telescope on 2013 December 15 shows possible signs of emerging helium absorption features. If confirmed, this would make iPTF13efs a member of the IIb subclass. Indeed, the SNID program (Blondin and Tonry, 2007, ApJ, 666, 1024) finds a good match to the Type IIb SN 1993J at 3 days before peak. Both spectra are publicly available through WISeREP (Yaron & Gal-Yam 2012).